Move Body into a direction

[Carli]

Hi,

I need to move a body into a direction only a few units. If the body collides, I want to have him at the closest not-colliding position.
How do I solve that problem? Shall I make a RayCast and a matrix manipilation?
Or is there an Engine function?

[JernejL]

Newtonupdate function performs a simulation step and automaticly does collision response to move bodies away.

[Carli]

but I want to do 2 movements a frame! i cannot do it over 2 frames, it would shake around (no stable graphics) and it would bounce back when i use a speed of 1000

[JernejL]

you could use newtonworldconvexcast to see how far you can move a object and then move it for desired or minumum distance there.

[Carli]

Code: Select all

const dFloat* target - Destination of the casted object in global space (convex cast does not support rotations).

is it a 3 float vector? or a matrix? (i hate C semi-typed pointers)

an example code would be helpful, the documentation is confusing.

Edit: what is the new object position when i move an object a few units until it will collide?

[Carli]

It causes a SIGSEGV
i don't know what i'm making wrong.
i think the pascal interface is still wrong - in C++ it returns an int, in pascal it's a procedure.

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function PathFree(home: PExecClass; pars:PData):TData; cdecl;
const lol:array[0..3] of single=(0,0,0,0);
var force:array[0..2] of single;
    matrix: array[0..3,0..3] of single;
    info: array of NewtonWorldConvexCastReturnInfo;
    o:TWorldObject;
    col:PNewtonCollision;
    i:integer; max,len:single;
type pvec3=^TVec3;
begin
 result:=novalue;
 o:=GetWObject(home);
 if o<>nil then begin
  NewtonBodyGetMatrix(o.newton,@matrix[0][0]);
  force[0]:=pars[0].float;
  force[1]:=pars[1].float;
  force[2]:=pars[2].float;
  max:=Vlen(force);
  force:=ApplyMatrixToVec3(matrix,force); //Richtung - gedreht zum Objekt
  setlength(info,128);
  col:=NewtonBodyGetCollision(o.newton);
  if col=nil then writeln('lol');
  i:=length(info);
  i:=NewtonWorldConvexCast(GetLogic(home).world,@matrix[0][0],@force[0],col,@lol[0],o,@myprefilter,@info[0],i,0);
  setlength(info,i);
  for i:=0 to high(info) do begin
   len:=vlen(SubtractVector(PVec3(@info[i].m_point[0])^,force));
   if len<max then begin
    result.int:=1;
    max:=len;
   end;
  end;
 end;
end;


what is the HitParam? it's not documented. i used 0,0,0,0 instead. How many components do the float *variables have?

[Carli]

now I checked the parameters (* all from old posts), but there is still the SIGSEGFault

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function myprefilter(const body : PNewtonBody; const collision : PNewtonCollision; userData : Pointer) : cardinal; cdecl;
begin
 result:=integer(TWorldObject(userData).newton<>body);
end;
function vlen(v:TVec3):single;
begin
 result:=sqrt(v[0]*v[0]+v[1]*v[1]+v[2]*v[2]);
end;

function PathFree(home: PExecClass; pars:PData):TData; cdecl;
var
    matrix: TMatrix4;
    pos, force: TVec3;
    info: array of NewtonWorldConvexCastReturnInfo;
    o:TWorldObject;
    col:PNewtonCollision;
    i:integer; max,len, lol:single;
type pvec3=^TVec3;
begin
 result:=novalue;
 o:=GetWObject(home);
 if o<>nil then begin
  NewtonBodyGetMatrix(o.newton,@matrix[0][0]); //Matrix holen
  pos:=SetVector(pars[0].float,pars[1].float,pars[2].float); //Position holen
  force:=ApplyMatrixToVec3(matrix,pos); //Zielposition
  max:=Vlen(pos); //größte erlaubte Wegstrecke
  pos:=ApplyMatrixToVec3(matrix,NullTVec3); //eigene Position
  setlength(info,128); //Die Kollisionsinfos anlegen
  col:=NewtonBodyGetCollision(o.newton);
  i:=length(info);
  i:=NewtonWorldConvexCast(GetLogic(home).world,@matrix[0][0],@force,col,@lol,o,@myprefilter,@info[0],i,0);
  setlength(info,i);
  for i:=0 to high(info) do begin
   len:=vlen(SubtractVector(PVec3(@info[i].m_point[0])^,pos));
   if len<max then begin
    result.int:=1;
    max:=len;
   end;
  end;
 end;
end;

maybe you forgot to set the call convention to cdecl???

[Carli]

or maybe the pascal header is wrong?
i don't know what the default call convention of your C++ is, but i think it's not cdecl.

what's the fault?

[JernejL]

From my game - just checks if anythint is in front of a car using convex casting, this code 100% works, there's even gl rendering debug code that can help you.

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function Tcar.check_obstacles(dist: single): boolean;
var
  tvec:      Vector;
  tmatrix:   Tmatrix4f;
  hitparams: array[0..31] of NewtonWorldConvexCastReturnInfo;
  hitparamsVecs: array[0..31] of VectorIdx;
//  info:      NewtonWorldConvexCastReturnInfo;
  x:      integer;
begin

  tmatrix := Self.matrix;
  tmatrix[3][2] := tmatrix[3][2] + 0.2;
  Move(tmatrix[3], tvec, sizeof(tvec)); // get just the location

  tvec := addVectors(tvec, MakeXYvectorFromRotation(radtodeg(heading) + 270, dist));
  {
  i      := find_any_car_near(tvec, dist * 2);
  Result := (i <> -1) and (Self.index <> i);
  }

  fillchar(hitparams, sizeof(hitparams), 0);
  //fillchar(hitparamsVecs, sizeof(hitparamsVecs), 0);

  x := NewtonWorldConvexCast(NWorld, @tmatrix, @tvec, NewtonBodyGetCollision(self.CarBody), @hitparamsVecs[0], self.CarBody, ignoreudbody, @hitparams[0], 32, 0);

{$ifdef debug_convexcast}
  glDisable(gl_texture_2d);

  glColor4f(1, 0, 0, 1);

  glLineWidth(3);

  glBegin(gl_line_loop);

  for i := 0 to x do
    if hitparams[i].m_point[0] <> 0 then
      glVertex3fv(@hitparams[i].m_point[0]);

  glend;

  glenable(gl_texture_2d);
{$endif}

  Result := x > 0;

end;

And this is dll import line, it is correct and works as i'm using it and it doesn't break:

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   function NewtonWorldConvexCast (const newtonWorld: PNewtonWorld; const matrix: PFloat; const target: PFloat; const shape: PNewtonCollision; hitParam: PFloat; userData: Pointer;
                      prefilter: PNewtonWorldRayPrefilterCallback; info: PNewtonWorldConvexCastReturnInfo; maxContactsCount: integer; threadIndex: integer): integer; cdecl; external newtondll;

[Carli]

aah i mixed the order of hitparam and userdata and also gave just one float at hitparam. Thanks.

(Maybe someone would specialize the float *to a more meaningful datatype)

[JernejL]

It really is just a pointer to a array of vector3f floats..

[Stucuk]

PFloat generally means that its more than 1 float and generally a 3f like Delfi said. Its rare in Newton for a PFloat to not be more than one float(Haven't checked to see if there is any that are just 1 float).

[Carli]

yes, but for me it wasn't clear that the first float *is a matrix, the second *one is a vector3f, the third is a field of n floats....